Can ghc treat certain specified warnings as errors and others as warnings?

Question

Can ghc somehow be convinced to treat certain types of warnings as errors and others as warnings, while still reporting them?

I hoped, this would be possible with something like this:

ghc -Werror -fwarn-missing-methods -Wwarn -fwarn-missing-signatures

, but I had no luck with that. (I think gcc doesn't support this either.)

Answer 1

Note that starting GHC 8.2.1, this feature exists! It was described by Trac ticket #11219 and now you can do ghc -Werror=missing-methods -Wmissing-signatures!